III International Conference

PP-I-36CRITICAL PHENOMENA FOR LANGMUIR-HINSHELWOOD MECHANISMMyshlyavtsev A.V. 1, 2 , Myshlyavtseva M.D. 11Omsk State Technical University, Omsk, Russia2 Institute of Hydrocarbons Processing SB RAS, Omsk, RussiaE-mail: myshl@omgtu.ruThe adsorbate - adsorbate lateral interaction influence on the steady-state multiplicitydomain and possible self-sustained oscillations of reaction rate for Langmuir-Hinshelwoodmechanism has been studied. We considered a lattice gas model on square, hexagonal andhoneycomb lattices as a model of adsorbed overlayer. The number of the internal steady stateswas shown to come up to eleven. The self-sustained oscillations of reaction rate arising as theresult of Andronov-Hopf’s bifurcation have been found for some sets of lateral interactions.One of the most important model mechanism of the heterogeneous catalysis is the wellknown three steps Langmuir-Hinshelwood (LH) mechanismA 2+ 2Z ↔ 2AZ; B + Z ↔ BZ; AZ + BZ → AB + 2Z,(1)where AZ and BZ are the adsorbed species on the catalyst Z, and A 2 , B and AB the gasphase substances. The conventional mean-field (MF) kinetic equations can be written as⎪⎧dx / dt = 2kP⎨⎪⎩ dy / dt = k2PBA( 1−x − y)( 1−x − y)−1 22k− 2k−2−1xy − k32− k xyxy,PAwhere x and y are the adsorbate concentrations,2k , − 1k−2andk33(2)andPBthe reactant pressures, k , k 1 2 ,the rate constants for adsorption, desorption and reaction, respectively; t is( lg P )A, lg PBtime. There exist the steady-state multiplicity domain in the plane2. This domaincontains two internal steady states [1]. The equations (2) ignore the non-ideality of surfacerate processes. We consider the MF equations incorporating the adsorbate-adsorbate lateralinteractions via the coverage dependence of the rate constants. In the frameworks of the latticegas model and transition state theory there are exact expressions for these constants [2]. Wehave done the analysis of the lateral interaction effect on the steady-state multiplicity domainand possibility of self-sustained oscillation appearance for LH mechanism on the squarelattice in the previous works. The kinetic behavior was shown to become essentially morecomplex than for ideal adsorbed overlayer [3]. The goal of the present work is the comparisonof the results obtained for the different lattice types such as the square, hexagonal andhoneycomb lattices. We consider the same lattice gas model [3] on the square, hexagonal and72